Effect of antibiotic concentration on the killing of Staphylococcus aureus and Enterococcus faecalis: comparison of the novel penem, Men 10700, with other beta-lactam antibiotics.
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BACKGROUND: This study was prompted by the increasing role of E. faecalis in hospital acquired infections, their morbidity and mortality and the development of resistances. The aim of the study was to define the epidemiological features, the predictive factors of bacteremia and the mortality prognosis in a group of patients with E. faecalis bacteremia. METHODS: The clinical and epidemiological features on admission, after 3 days and one week of therapy and one month after therapy were evaluated in 57 cases of true E. faecalis bacteremia. The effectiveness of therapy was assessed by the rate of clinical and microbiological cures, deaths and survivals. RESULTS: The incidence of E. faecalis bacteremia was 5.9%. 78% of them were hospital acquired, with unknown source in 31%. Generally, they developed in surgical services and usually the patients had received antibiotic treatment or instrumentation. 63% of bacteremias were monomicrobial. Male sex, hospitalization (particularly in surgical or intensive care services), underlying disease of rapidly fatal prognosis, the previous use of third generation cephalosporins and/or ciprofloxacin, and previous instrumentation or surgery were found to be predictive factors of bacteremia. On the other hand, underlying disease with rapidly fatal prognosis, with initial poor or critical clinical condition, the previous use of wide spectrum antibiotics, polymicrobial bacteremia, and the presence of leukocytosis or complications were significantly associated with a higher mortality. The resistance rates ranged between 42% to kanamycin and 1% to amikacin. CONCLUSIONS: In view of the results, a better knowledge of the predictive and prognostic factors of E. faecalis bacteremia is required for prevention and treatment.
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The E. faecalis cytolysin represents a new class of cytolytic agents which are related to a family of antibacterial peptides termed lantibiotics. Despite considerable similarity at the genetic level, the E. faecalis cytolysin differs from the lantibiotics in several respects. First, the E. faecalis cytolysin consists of two dissimilar precursors, both of which are required to effect target cell lysis. A second important difference is that the E. faecalis cytolysin is active against eukaryotic as well as Gram-positive prokaryotic cells. Originally identified as a haemolysin [32], the E. faecalis cytolysin has been shown to make a contribution to bacterial virulence in endocarditis [8, 33] and endophthalmitis [7] models, and the cytolytic phenotype is enriched among clinical isolates of the organism [2, 3]. Similarities between the E. faecalis cytolysin and lantibiotics such as nisin (which is used as a food preservative in several countries [34] and is the subject of continuing attempts at rational design of lantibiotic-based food preservatives [25]), and the observation of an association between the E. faecalis cytolysin and bacterial virulence indicate that it may be possible to engineer lantibiotics to a point where undesired toxic or cytolytic activities will arise. Further comparison of the chemical, structural and biological properties of the E. faecalis cytolysin and classical lantibiotics will define these limits.
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Single strain regression analysis was performed on PDM II medium for E. faecalis with 10, 30 and 120 micrograms gentamicin disks using E. faecalis, strain ATCC 29212 as the reference. This method permits the calculation of zone diameters corresponding to different MIC values for different disk contents. The lack of discrimination between normal low-level resistant strains and high-level resistance using the 10 micrograms disk was confirmed. However, both the 30 micrograms and 120 micrograms disks seemed to provide a separation of the normal low-level gentamicin-resistant population from strains with increased resistance. Since the 30 micrograms disk is used routinely in some countries, there should be no need for an extra high content disk in these laboratories. This was confirmed when 96 clinical isolates of E. faecalis were analysed and the results of routine disk diffusion tests were compared with the MIC values. Two of the strains showed high-level gentamicin resistance (greater than 2000 mg/l) and produced no zone of inhibition. The other 94 isolates showed gentamicin MIC values between 4-16 mg/l, and 72 of the MIC results were 8 mg/l. The zone diameters for these strains ranged between 15 and 25 mm with a mean of 18.2 and a median value of 18 mm. In order to include statistical considerations of the zone size populations for setting of breakpoints, a study of gentamicin zone size distributions was performed for several bacterial species. Inhibition zone diameter values around the 30 micrograms gentamicin disk for 2079 clinical isolates of E. faecalis, 2268 S. aureus, 3201 E. coli and 547 strains of P. mirabilis from different years were plotted as histograms. Tests for agreement with a Gaussian distribution showed that the histograms were slightly peaked and skewed towards higher zone values. Parametric and non-parametric statistical tests were compared and the results showed that means and medians were very similar and that parametric fractile estimations at the lower end of the histogram populations were conservative and could be used in view of a slightly lower rate of false resistance. The 1% parametric fractile of 12 mm was selected as a suitable breakpoint for the identification of normal, low-level resistant isolates of E. faecalis using the standardized disk test of the Swedish Reference Group for Antibiotics.
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Serotyping was conducted of E. faecalis strains isolated from various clinical specimens, and the distribution of the serovars was investigated. To date, 21 serovars of E. faecalis have been identified. The most common serovars in Japanese 770 strains were types 2 (30.6%), 7 (13.9%), 1 (12.2%) and 4 (6.9%), and these four serovars accounted for 63.6% of the total strains. The most common serovars in USA 200 strains were types 1 (22.5%), 4 (14.5%) and 2 (14.0%). The most common serovars in UK 65 strains were types 2 (24.6%), 4 (13.8%) and 9 (7.7%). The distribution of E. faecalis serovars differ as a function of the country of origin. Next, serological classification was performed for E. faecalis strains isolated from various Japanese clinical specimens. For the strains obtained from the urine, the most common serovars were types 2 (32.7%) and 7 (14.6%). Similarly, the most common serovars of the strains isolated from the various other clinical specimens were as follows: types 7 (35.0%) and 2 (15.0%) from pus; types 7 (44.4%) and 2 (33.3%) from sputum; types 2 (22.3%) and 1 (13.1%) from blood; and types 2 (34.9%) and 1 (27.9%) from the vaginal smear. It had no definite pattern for the distribution of serovars. The distribution of serovars varied in accordance with isolated years. Accordingly, the data obtained in these studies revealed that the distributions of E. faecalis serovars differ as a function of the geographical area of origin, the clinical specimen of origin and the year of origin. This approach is useful for serological classification of E. faecalis strains, and it is thought that it will be useful for epidemiological studies of this bacterium.
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AIM: This study sought to clarify the mechanisms that enable E. faecalis to survive the high pH of calcium hydroxide. METHODOLOGY: E. faecalis strain JH2-2 was exposed to sublethal concentrations of calcium hydroxide, with and without various pretreatments. Blocking agents were added to determine the role of stress-induced protein synthesis and the cell wall-associated proton pump. RESULTS: E. faecalis was resistant to calcium hydroxide at a pH of 11.1, but not pH 11.5. Pre-treatment with calcium hydroxide pH 10.3 induced no tolerance to further exposure at pH 11.5. No difference in cell survival was observed when protein synthesis was blocked during stress induction, however, addition of a proton pump inhibitor resulted in a dramatic reduction of cell viability of E. faecalis in calcium hydroxide. CONCLUSIONS: Survival of E. faecalis in calcium hydroxide appears to be unrelated to stress induced protein synthesis, but a functioning proton pump is critical for survival of E. faecalis at high pH.
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A simple, low cost device for electrotransformation has been designed and constructed. The cost of the circuit was only $150. Maximum field strength of 12,000 V/cm with an actual time constant up to 11 msec was obtained with a newly designed circuitry and a 0.1-cm electrode gap cuvette. Eschericia coli strains DH1, DH5 alpha, and LE392 were transformed at an efficiency of 10(9)/micrograms DNA with plasmids pUC18 and pBR322. E. faecalis strain OG1X was transformed at an efficiency of 0.9 x 10(5)/micrograms DNA without treatment with glycine.
The aim of this study was to compare the efficacy of root canal irrigants against E. faecalis biofilms using a novel in vitro testing system. Biofilms grown in a flow cell system were submerged in test irrigants for either 1 or 5 minutes. Statistical analysis revealed a significant relationship between test agent and percentage kill of the biofilm bacteria (P < 0.05). No statistically significant relationship between time and percentage kill was found. The percentage kill of the biofilm bacteria was: 6% NaOCl (>99.99%), 1% NaOCl (99.78%), Smear Clear (78.06%), 2% chlorhexidine (60.49%), REDTA (26.99%), and BioPure MTAD (16.08%). Post-hoc analysis showed a significant difference between 1% and 6% NaOCl, and all other agents including Smear Clear, 2% chlorhexidine, REDTA, and BioPure MTAD (P < 0.05). Within the parameters of this study, both 1% NaOCl and 6% NaOCl were more efficient in eliminating E. faecalis biofilm than the other solutions tested.
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